Think back to the last time you were hospitalised, in order to cure some medical problem which had arisen. It might have been for some minor operation, or for major surgical intervention. Your hospitalisation could have lasted a day, a week, a month.
Human life reflects the Newtonian principle that every action results in an equal and opposite reaction. When you give, you will receive. Every person, in every age, who has applied this has found it to be true.